Fabrication of High-Quality Co2FeSi/SiOxNy/Si(100) Tunnel Contacts Using Radical-Oxynitridation-Formed SiOxNy Barrier for Si-Based Spin Transistors

A high-quality Co 2 FeSi (CFS)/SiO x N y /Si tunnel junction was fabricated, in which the SiO x N y barrier layer was formed by radical oxynitridation of an Si(100) substrate and the CFS electrode was formed by silicidation of an Fe/Co/amorphous-Si multilayer deposited on the barrier layer. The ultrathin SiO x N y barrier layer completely blocked diffusion of Co and Fe atoms into the Si substrate during rapid thermal annealing (RTA) for the silicidation. X-ray diffraction investigations clarified that the CFS film on the ultrathin SiO x N y barrier layer exhibited a highly (110)-oriented texture structure and that the film had the L 2 1 structure with a high degree of L 2 1 order. High resolution cross-sectional transmission electron microscopy investigations revealed that the CFS/SiO x N y interface was atomically flat and that the crystal lattice of the CFS film was directly grown on the SiO x N y surface without degradation of the crystallinity at the interface.